runIO

runIO

If you just run IO.unsafeRunSync() in a test, it may not end and just hang. extras for hedgehog and cats-effect 3 (extras-hedgehog-ce3) can solve it with runIO.

def runIO(test: => IO[Result]): Result

To use runIO, your test needs to extend CatsEffectRunner

import hedgehog.runner._
import extras.hedgehog.ce3.CatsEffectRunner

object SomeSpec extends Properties with CatsEffectRunner {

then in your test, use runIO like

def test: Result = 
  runIO {
    // Your test
    val exected = ??? // A
    val actual = ??? // IO[A]
    actual.map(_ ==== expected) // IO[Result]
  }

or

def test: Property =
  for {
    n <- Gen.int(Range.linear(1, 100)).log("n")
  } yield runIO {
    // Your test
    val exected = ??? // A
    val actual = ??? // IO[A]
    actual.map(_ ==== expected) // IO[Result]
  }

Test Success Case

Use CatsEffectRunner and completeThen instead of unsafeRunSync().

import cats.effect._

import extras.hedgehog.ce3.CatsEffectRunner

import hedgehog._
import hedgehog.runner._

object SomeSpec extends Properties with CatsEffectRunner {
  
  override def tests: List[Test] = List(
    property("test with CatsEffectRunner and success case", testCatsEffectRunnerWithSuccessCase)
  )
  
  def testCatsEffectRunnerWithSuccessCase: Property = for {
    n <- Gen.int(Range.linear(Int.MinValue, Int.MaxValue)).log("n")
  } yield runIO {

    val expected = n
    val actual = IO(n)

    actual.map { actual =>
      actual ==== expected
    } // IO[Result]
  }
}

Test Error Case

If you want to test with IO which may result in some Exception thrown, you can use errorThen instead of unsafeRunSync() and Try.

import cats.effect._

import extras.hedgehog.ce3.CatsEffectRunner

import hedgehog._
import hedgehog.runner._

object SomeSpec extends Properties with CatsEffectRunner {

  override def tests: List[Test] = List(
    property("test with CatsEffectRunner and erro case", testCatsEffectRunnerWithErrorCase)
  )

  def testCatsEffectRunnerWithErrorCase: Property = for {
    message <- Gen.string(Gen.alphaNum, Range.linear(1, 10)).log("message")
    error <- Gen
      .element1(
        TestError.someTestError(s"Don't worry it's only a test error. $message"),
        TestError.anotherTestError(s"Don't worry it's only a test error. $message")
      )
      .log("error")
  } yield runIO {

    val expected = error
    val actual = IO.raiseError[Int](error)

    actual.attempt.map {
      case Left(actual) =>
        actual ==== expected
      case Right(r) =>
        Result.failure.log(s"Expected error $expected but got $r instead.")
    } // IO[Result]
  }

  sealed abstract class TestError(val message: String) extends RuntimeException(message)

  object TestError {
    final case class SomeTestError(override val message: String) extends TestError(message)
    final case class AnotherTestError(override val message: String) extends TestError(message)

    def anotherTestError(message: String): TestError = AnotherTestError(message)
    def someTestError(message: String): TestError = SomeTestError(message)

  }
}